Biology SL
Theme A: Unity and diversity — Theme A
- 1.
State three features common to all cells, according to cell theory.
[3 marks] · no calculator - 2.
Marking analysis: A learner attempts the following task: “State three features common to all cells, according to cell theory.” Their response addresses only this point: “States that all cells are bound by a plasma membrane that separates the interior from the environment.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 3.
Distinguish between prokaryotic and eukaryotic cells in terms of their genetic material and membrane-bound organelles.
[4 marks] · no calculator - 4.
Marking analysis: A learner attempts the following task: “Distinguish between prokaryotic and eukaryotic cells in terms of their genetic material and membrane-bound organelles.” Their response addresses only this point: “States that prokaryotic cells have a single circular DNA molecule that is not enclosed by a nuclear membrane, free in the cytoplasm.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] · no calculator - 5.
Outline two properties of water that make it important for living organisms.
[2 marks] · no calculator - 6.
Marking analysis: A learner attempts the following task: “Outline two properties of water that make it important for living organisms.” Their response addresses only this point: “States that water is a good solvent for polar and ionic substances, due to its polarity, allowing many biochemical reactions to occur in aqueous solution.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 7.
Outline two types of evidence used to support the theory of evolution.
[2 marks] · no calculator - 8.
Marking analysis: A learner attempts the following task: “Outline two types of evidence used to support the theory of evolution.” Their response addresses only this point: “States fossil evidence: fossils in successive rock strata show a chronological sequence of gradual change in organisms over geological time.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 9.
Outline the biological species concept and state one limitation of this definition.
[2 marks] · no calculator - 10.
Marking analysis: A learner attempts the following task: “Outline the biological species concept and state one limitation of this definition.” Their response addresses only this point: “States that a species is defined as a group of organisms that can interbreed and produce fertile offspring under natural conditions.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 11.
Explain the process of allopatric speciation.
[4 marks] · no calculator - 12.
Marking analysis: A learner attempts the following task: “Explain the process of allopatric speciation.” Their response addresses only this point: “States that a population becomes geographically separated into two groups by a physical barrier (e.g. a mountain range, river or ocean), preventing gene flow between them.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] · no calculator - 13.
Outline the principle of binomial nomenclature used in the naming of species.
[2 marks] · no calculator - 14.
Marking analysis: A learner attempts the following task: “Outline the principle of binomial nomenclature used in the naming of species.” Their response addresses only this point: “States that each species is given a two-part scientific name: the genus name followed by the species name (e.g. Homo sapiens).” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 15.
Explain how a cladogram uses shared derived characteristics to represent evolutionary relationships between species.
[3 marks] · no calculator - 16.
Marking analysis: A learner attempts the following task: “Explain how a cladogram uses shared derived characteristics to represent evolutionary relationships between species.” Their response addresses only this point: “States that a cladogram is a branching diagram that represents hypothesized evolutionary relationships based on shared characteristics.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 17.
Define biodiversity, and outline why biodiversity is important for ecosystem stability.
[2 marks] · no calculator - 18.
Marking analysis: A learner attempts the following task: “Define biodiversity, and outline why biodiversity is important for ecosystem stability.” Their response addresses only this point: “Defines biodiversity as the variety of life, including diversity within species (genetic diversity), between species, and of ecosystems.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 19.
Outline two human activities that threaten biodiversity, and for each, state the primary mechanism of harm.
[4 marks] · no calculator - 20.
Marking analysis: A learner attempts the following task: “Outline two human activities that threaten biodiversity, and for each, state the primary mechanism of harm.” Their response addresses only this point: “States habitat destruction (e.g. deforestation, land conversion for agriculture) as a first threat.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] · no calculator - 21.
Outline one strategy used in conservation biology to protect biodiversity, and explain how it addresses a specific threat.
[2 marks] · no calculator - 22.
Marking analysis: A learner attempts the following task: “Outline one strategy used in conservation biology to protect biodiversity, and explain how it addresses a specific threat.” Their response addresses only this point: “Outlines a valid conservation strategy, e.g. establishing protected areas/nature reserves, captive breeding programmes, or seed banks.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 23.
Outline the basic structure of DNA, referring to nucleotides and the double helix.
[3 marks] · no calculator - 24.
Marking analysis: A learner attempts the following task: “Outline the basic structure of DNA, referring to nucleotides and the double helix.” Their response addresses only this point: “States that DNA is composed of repeating subunits called nucleotides, each containing a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases (A, T, C, G).” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 25.
Explain why carbon is particularly suited to forming the wide variety of biological molecules found in living organisms.
[3 marks] · no calculator - 26.
Marking analysis: A learner attempts the following task: “Explain why carbon is particularly suited to forming the wide variety of biological molecules found in living organisms.” Their response addresses only this point: “States that a carbon atom can form four covalent bonds, allowing it to bond with up to four other atoms.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 27.
State the seven main taxonomic ranks used to classify organisms, in order from the broadest to the most specific.
[2 marks] · no calculator - 28.
Marking analysis: A learner attempts the following task: “State the seven main taxonomic ranks used to classify organisms, in order from the broadest to the most specific.” Their response addresses only this point: “States the correct order: kingdom, phylum, class, order, family, genus, species.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 29.
Outline the process of natural selection, using antibiotic resistance in bacteria as an example.
[4 marks] · no calculator - 30.
Marking analysis: A learner attempts the following task: “Outline the process of natural selection, using antibiotic resistance in bacteria as an example.” Their response addresses only this point: “States that genetic variation exists naturally within a population, e.g. some bacteria may already carry a mutation providing antibiotic resistance.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] · no calculator - 31.
In a population, 9% of individuals show a recessive phenotype (genotype aa). Assuming the population is in Hardy-Weinberg equilibrium, (a) calculate the frequency of the recessive allele (q), (b) calculate the frequency of the dominant allele (p), and (c) calculate the percentage of the population that are heterozygous carriers (Aa).
[5 marks] - 32.
Marking analysis: A learner attempts the following task: “In a population, 9% of individuals show a recessive phenotype (genotype aa). Assuming the population is in Hardy-Weinberg equilibrium, (a) calculate the frequency of the recessive allele (q), (b) calculate the frequency of the dominant allele (p), and (c) calculate the percentage of the population that are heterozygous carriers (Aa).” Their response addresses only this point: “States the Hardy-Weinberg equations: p + q = 1 and p² + 2pq + q² = 1.” Evaluate the response against the complete 5-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[5 marks] - 33.
The cladogram below shows the evolutionary relationships of four species, with species W and X sharing the most recent common ancestor, and this clade sharing an earlier common ancestor with species Y, which in turn shares an even earlier common ancestor with species Z: (((W,X),Y),Z). State which two species are most closely related, and explain how a cladogram represents evolutionary relationships using branching points.
[3 marks] · no calculator - 34.
Marking analysis: A learner attempts the following task: “The cladogram below shows the evolutionary relationships of four species, with species W and X sharing the most recent common ancestor, and this clade sharing an earlier common ancestor with species Y, which in turn shares an even earlier common ancestor with species Z: (((W,X),Y),Z). State which two species are most closely related, and explain how a cladogram represents evolutionary relationships using branching points.” Their response addresses only this point: “States that species W and X are most closely related, since they share the most recent common ancestor.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 35.
A sample of double-stranded DNA is found to be 30% adenine. (a) State the percentage of thymine in the sample. (b) Calculate the percentage of guanine and the percentage of cytosine in the sample, assuming they are present in equal amounts.
[3 marks] - 36.
Marking analysis: A learner attempts the following task: “A sample of double-stranded DNA is found to be 30% adenine. (a) State the percentage of thymine in the sample. (b) Calculate the percentage of guanine and the percentage of cytosine in the sample, assuming they are present in equal amounts.” Their response addresses only this point: “States that, by complementary base pairing, adenine always pairs with thymine, so thymine must also be 30%.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks]